The two sides have been negotiating since October and have said they expect a new collective bargaining agreement in time for the upcoming season. A session was held Sunday under the auspices of the Federal Mediation and Conciliation Service.
The league said Monday that regional training sessions for replacement refs would begin later this month "to ensure that there is no disruption to NFL games this season."
The NFL's search would target retired college officials and perhaps current ones who would be qualified to work professional games. In 2001, the league used replacement officials for one preseason game, then the first weekend of the regular season.